GB/T 11026.8-2025Electrical insulating materials - Thermal endurance properties - Part 8: Determination of thermal endurance indices(TI and RTI) of an insulating material using the fixed time frame method (English PDF)

Foreword

This document complies with the provisions of GB/T 1.1-2020 "Standardization Work Guidelines Part 1: Structure and Drafting Rules of Standardization Documents". Drafting.

This document is Part 8 of GB/T 11026 "Heat Resistance of Electrical Insulation Materials". GB/T 11026 has already published the following parts.

---Part 1: Aging Procedures and Evaluation of Test Results;

---Part 2: Selection of Test Judgment Criteria;

---Part 3: Procedures for calculating heat resistance characteristic parameters;

---Part 4: Aging Oven - Single Chamber Oven;

---Part 5: Precision ovens with aging temperatures up to 300°C;

---Part 6: Aging Ovens - Multi-chamber Ovens;

---Part 7: Determining the Relative Temperature Index (RTI) of Insulating Materials;

---Part 8: Determining the heat resistance index (TI and RTI) of insulating materials using the fixed time limit method;

---Part 9: Guidelines for calculating heat resistance using simplified procedures;

---Part 10: Guidelines for accelerating the determination of the relative heat resistance index (RTEA) based on activation energy calculations using analytical experimental methods.

This document replaces GB/T 11026.8-2014 "Electrical Insulation Materials - Heat Resistance Part 8: Determination of Insulation Materials by Fixed Time Limit Method".

The heat resistance index (TI and RTE) of the material, compared with GB/T 11026.8-2014, has undergone major technical changes except for structural adjustments and editorial modifications. The following is a simplified version.

a) The standard "GB/T 11026.1-2003" has been changed to "GB/T 11026.1" (see 4.1, 7.2.2 and 13.3, and 4.1.1, 7.2.2 and 13.3 in the 2014 edition);

b) The standard "GB/T 11026.3-2006" has been changed to "GB/T 11026.3-2025" (see 13.1, 2014 edition).

c) The standard "GB/T 21223-2007" has been changed to "GB/T 21233" (see 6.1.1, 2014 version of 6.1.1);

d) The standard "IEC 60216-5" has been changed to "GB/T 11026.7-2025" (see Chapter 9, 2014 edition, 13.2);

e) The term and definition of "electrical insulation materials" have been added (see 3.1.1);

f) The term "estimated heat resistance index" has been changed to "estimated temperature index" (see 3.1.2, 3.1.1 in the 2014 version);

g) The term "Materials to be Evaluated" has been changed to "EIM to be Evaluated" (see 3.1.5, 3.1.4 in the 2014 version);

h) The term "benchmark material" has been changed to "benchmark EIM" (see 3.1.8, 3.1.7 in the 2014 version);

i) The term "relevant time" has been changed to "relevant time of RTI" (see 3.1.10, 3.1.9 in the 2014 version);

j) Changed "Relevant Time" to "TI Relevant Time" (see 3.1.11, 3.1.10 in the 2014 version);

k) The term "relative heat resistance index" has been changed to "relative temperature index" (see 3.1.19, 3.1.18 in the 2014 version);

l) The term "Relative Heat Resistance Index (RTE)" has been changed to "Relative Temperature Index (RTI)" (see full text, 2014 edition).

m) The definition of "temperature index" has been changed (see 3.1.23, 3.1.22 in the 2014 version);

n) Added "TI's report format derived for time periods other than 20000h" (see 7.2.2);

o) The format for presenting experimental results in the "Results" section has been changed (see 13.2, 2014 version 13.2);

p) The term "Dataset (ATE)" in Appendix F has been changed to "Dataset (ATI)" (see Appendix F, Appendix F of 2014).

This document is modified to adopt IEC 60216-6:2022 "Electrical insulating materials - Heat resistance - Part 6: Determination of the heat resistance index (TI and RTI) of insulating materials by the fixed time limit method".

The technical differences between this document and IEC 60216-6:2022, and the reasons therefor, are as follows.

a) IEC 60216-1:2013 (see Chapter 1) has been replaced with the normatively referenced GB/T 11026.1 to improve operability;

b) IEC 60216-2 (see Chapters 1 and 5) has been replaced with the normatively referenced GB/T 11026.2 to improve operability;

c) IEC 60216-4-1 (see 5.7.1) has been replaced with the normatively referenced GB/T 11026.4 to increase operability;

d) IEC 60216-4-2 (see 5.7.1) has been replaced with the normatively referenced GB/T 11026.5 to increase operability;

e) IEC 60216-4-3 (see 5.7.1) has been replaced with the normatively referenced GB/T 11026.6 to increase operability;

f) IEC 60212 (see 5.7.2) has been replaced with the normatively referenced GB/T 10580 to increase operability;

g) IEC 60493-1 (see 6.1.1) has been replaced with the normatively referenced GB/T 21223.1 to increase operability;

h) The requirement of 6.8 in IEC 60216-1:2013 has been revised to the requirement of report format in GB/T 11026.1 (see 7.2.2). Increase operability.

The following editorial changes have been made to this document.

---In accordance with the GB/T 11026 series standard numbering, part 6 of the original English name has been changed to part 8.

Introduction

GB/T 11026 aims to establish test procedures, test judgment criteria, aging ovens, and relative standards for the heat resistance of electrical insulation materials. Procedures for evaluating heat resistance index, etc. Currently, GB/T 11026 consists of the following 10 parts.

---Part 1: Aging Procedures and Evaluation of Test Results. The aim is to establish aging procedures for evaluating the heat resistance of insulating materials and to improve... How to evaluate the results of aging tests.

---Part 2: Selection of Test Judgment Criteria. The purpose is to propose criteria for judging the endpoint of thermal aging tests on insulating materials.

---Part 3: Procedures for calculating heat resistance characteristic parameters. The purpose is to establish the method for obtaining heat resistance characteristic parameters using GB/T 11026.1 and GB/T 11026.2.

The experimental data were used to derive a calculation program for the heat resistance characteristic parameters.

---Part 4: Aging Oven - Single Chamber Oven. The purpose is to specify that the temperature used for heat resistance aging tests should be 20°C higher than ambient temperature.

A single-chamber oven that operates over the entire or a portion of the 500°C temperature range.

---Part 5: Precision ovens with aging temperatures up to 300°C. The purpose is to specify the environmental conditions used in heat resistance aging tests.

A precision drying oven that operates within a temperature range of 20°C to 500°C, either in the entire range or in part of it.

---Part 6: Aging Oven - Multi-chamber Oven. The purpose is to specify that the temperature used for heat resistance aging tests should be 20°C higher than ambient temperature.

A multi-chamber oven that operates over the entire or a portion of the 500°C temperature range.

---Part 7: Determination of the Relative Temperature Index (RTI) of Insulation Materials. The aim is to establish the use of GB/T 11026.1 and... The test and calculation procedures for deriving the relative temperature index from the test data obtained in GB/T 11026.2.

---Part 8: Determining the Heat Resistance Index (TI and RTI) of Insulating Materials Using the Fixed Time Limit Method. The aim is to establish the use of fixed time limits... The experimental and calculation procedures for deriving the heat resistance index were developed.

---Part 9: Guidelines for Calculating Heat Resistance Using Simplified Procedures. The aim is to establish simplified procedures for obtaining the heat resistance properties of insulating materials.

---Part 10: Guidelines for accelerating the determination of the relative heat resistance index (RTEA) based on activation energy calculations using analytical experimental methods.

The key is to establish a lifetime point based on the thermal degradation activation energy obtained from thermal analysis methods and conventional thermal aging tests, and to evaluate... Procedure for determining the relative heat resistance index of insulating materials.

1 Scope

Experimental and calculation procedures for deriving the temperature index (TI) and relative temperature index (RTI).

According to FTFM, the aging process occurs within a few fixed time periods, each time using an appropriate aging temperature point, at the corresponding time... At the end of the interval, the performance of the sample is measured. This method differs from the procedure in GB/T 11026.1, where the aging process... The process is completed at a few fixed temperatures, while performance measurements are taken after the aging time, based on the aging process.

The diagnostic tests used in the fixed-time method are only applicable to destructive tests, not to non-destructive tests or validation tests.

According to FTFM, the TI and RTI obtained from the test data in this document conform to GB/T 11026.1 and GB/T 11026.2, and have been verified.

The calculation procedures and statistical tests have been revised from the corresponding procedures in GB/T 11026.3 and GB/T 11026.7.

2 Normative references

The contents of the following documents, through normative references within the text, constitute essential provisions of this document. Dated citations are not included.

For references to documents, only the version corresponding to that date applies to this document; for undated references, the latest version (including all amendments) applies. This document.

GB/T 10580 Standard conditions for solid insulating materials before and during testing (GB/T 10580-2015, IEC 60212. 2010, IDT)

GB/T 11026.1 Electrical insulating materials - Heat resistance - Part 1: Aging procedures and evaluation of test results (GB/T 11026.1-2016, IEC 60216-1:2013, IDT)

GB/T 11026.2 Electrical insulating materials - Heat resistance - Part 2: Selection of test criteria (GB/T 11026.2-2012, IEC 60216-2:2005, IDT)

GB/T 11026.3-2025 Electrical insulating materials - Heat resistance - Part 3: Procedure for calculating characteristic parameters of heat resistance (IEC 60216-3:2021, MOT)

Note: There are no technical differences between the content referenced in GB/T 11026.3-2025 and the content referenced in IEC 60216-3:2021.

GB/T 11026.4 Heat resistance of electrical insulating materials - Part 4: Aging ovens - Single-chamber ovens (GB/T 11026.4-2012, IEC 60216-4-1:2006, IDT)

GB/T 11026.5 Heat resistance of electrical insulating materials - Part 5: Precision ovens with aging oven temperatures up to 300°C (GB/T 11026.5-2010,IEC 60216-4-2:2000,IDT)

GB/T 11026.6 Electrical insulating materials - Heat resistance - Part 6: Aging ovens - Multi-chamber ovens (GB/T 11026.6-2010, IEC 60216-4-3:2000, IDT)

GB/T 11026.7-2025 Electrical insulating materials - Heat resistance - Part 7: Determination of the relative temperature index (RTI) of insulating materials (IEC 60216-5:2022, MOT)

Note: There are no technical differences between the content referenced in GB/T 11026.7-2025 and the content referenced in IEC 60216-5:2022.

GB/T 21223.1 Guidelines for Statistical Analysis of Aging Test Data - Part 1: Based on the Average Value of Normally Distributed Test Results The above method (GB/T 21223.1-2015, IEC 60493-1:2011, IDT)